Capacitors including interacting separators and surfactants

ABSTRACT

The present invention relates generally to capacitor cells and the utilization of separator materials that interact with one or more surfactants in such cells. More specifically, the present invention is related to capacitor cells that include separators that are impregnated with a surfactant or that absorb and/or interact with a surfactant that is included in an electrolyte placed within the capacitor cell.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This patent disclosure claims the benefit of prior provisionalU.S. patent application Ser. No. 60/474,800 (Atty Dkt 539.2000.0),invented by Norton et al., filed 30 May 2003, and entitled, “CapacitorCells Including Enhanced Separator Systems and Materials”—the contentsof which are fully incorporated herein.

FIELD OF THE INVENTION

[0002] The present invention relates generally to capacitor cells andthe utilization of separator materials that interact with one or moresurfactants in such cells. More specifically, the present invention isrelated to capacitor cells that include separators that are impregnatedwith a surfactant or that absorb and/or interact with a surfactant thatis included in an electrolyte placed within the cell.

BACKGROUND OF THE INVENTION

[0003] A capacitor cell typically comprises an anode having a dielectriclayer, a separator, a cathode, and an electrolyte solution. The anodeand cathode often comprise stacked or coiled metallic foil membersalthough pressed, sintered and formed powdered metal anodes are knownand used in the art. The energy of a capacitor cell is stored in theelectromagnetic field generated by opposing electrical charges separatedby the dielectric layer disposed on the surface of the anode. Etchingmay be used to increase the surface area of the anode, as the energystored by the cell is proportional to the surface area of the anode. Adielectric oxide layer is formed on the anode when a voltage is appliedin an electrolytic solution. The dielectric layer insulates the anodefrom the cathodic electrolytic solution, allowing charge to accumulate.The separator holds the anode and cathode foils or powdered slug-typeanodes apart to maintain charge and prevent short-circuiting. In oneembodiment, the anode/separator/cathode laminate is typically rolled upto form a cylindrical coiled member and encased, with the aid ofsuitable insulation, in an aluminum tube that is subsequently sealedwith rubber material. In such embodiments it is imperative that thecathode foil and anode foil be precisely positioned opposite each otheron the separator material and be adequately separated by this samematerial.

[0004] An alternative design, commonly used in implantablecardioverter-defibrillators (ICDs), are flat (e.g., stacked electrode),compact aluminum electrolytic capacitors. These flat capacitors havebeen developed to overcome some disadvantages inherent in commercialcylindrical capacitors. For example, U.S. Pat. No. 5,131,388 to Plesset. al. discloses a relatively volumetrically efficient flat capacitorhaving a plurality of planar layers arranged in a stack. Each layercontains an anode layer, a cathode layer and means for separating theanode layers and cathode layers (such as paper). The anode layers andthe cathode layers are generally comprised of foil plates of anode orcathode material and are usually electrically connected in parallel. Ina paper “High Energy Density Capacitors for Implantable Defibrillators”presented at CARTS 96: 16th Capacitor and Resistor Technology Symposium,Mar. 11-15, 1996, several improvements in the design of flat aluminumelectrolytic capacitors are described, such as the use of an embeddedanode layer tab and solid adhesive electrolyte. Further advances in flatelectrolytic capacitors are found in U.S. Pat. No. 6,006,133, issued toLessar et al., which is incorporated by reference.

[0005] For flat, powdered metal, or cylindrical capacitor cells, it isnecessary that the anode and cathode remain separated. A minimumseparation between the anode and cathode must be maintained to preventarcing between the anode and cathode, and to allow charge to accumulatewithout short-circuiting. In cylindrical cells, the anode and cathodefoils are aligned precisely with a separator positioned between them andcoiled tightly to prevent movement of the anode, cathode and separatorduring subsequent processing and use. Spacing is typically maintained atthe electrode edges as well by providing separator overhang at the topand bottom of the anode and cathode winding, to prevent short-circuitingto the casing. In flat capacitor cells, anode to cathode alignment istypically maintained through the use of internal alignment posts orscrews (as described, for example, in U.S. Pat. No. 6,006,133 to Lessaret al.). Alignment of the anode and cathode plates in flat capacitorcells again can be somewhat problematic in that the plates are generallysmall and difficult to maneuver and maintain in position during assemblyof the capacitor cell.

[0006] Maintaining a proper distance between cell components is thus oneof the prime functions of a separator. A separator must be resistant todegradation, have sufficient thickness to maintain inter-electrodeseparation without interfering with cell high performance, and exhibitsufficient surface energy such that electrolyte wettability andabsorption are augmented. The enhancement of the wettability andabsorption properties is desired since such enhancement is likely toreduce the equivalent series resistance of the cell thereby increasingthe fraction of the stored energy delivered to the medical device.However, the separator must also have an electrical resistivitysufficiently high to prohibit short circuit current from flowingdirectly between the electrodes through the separator and tortuosity toprovide adequate ionic transfer. These requirements are balanced by theneed for the separator to have porosity sufficient to maintain electrodeseparation while allowing ionic transfer to occur unimpeded within theelectrolyte during discharge. Additionally, the separator must havesufficiently strong tensile properties to facilitate cell fabricationand to withstand internal cell stresses due to changes in electrodevolume during charge/discharge cycles.

[0007] Separators are generally made from a roll or sheet of separatormaterial, and a variety of separator materials have been found to beeffective. Paper, particularly Kraft paper, is a cellulose-basedseparator material that is commonly used. Cellulose separator materialsare manufactured with high chemical purity. The total thickness ofcellulose separators employed between anode and cathode plates will varywith the voltage rating of the capacitor structure and the type ofelectrolyte employed but, on the average, the thickness varies from0.003″ to 0.008″ in connection with capacitors rated at from 6 volts to600 volts.

[0008] A common alternative to paper separators are polymericseparators. Generally, polymeric separators are either made ofmicroporous films or polymeric fabric. An example of a microporous filmseparator is a separator comprising polytetrafluoroethylene, disclosedin U.S. Pat. No. 3,661,645 to Strier et al. U.S. Pat. No. 5,415,959 toPyszeczek et al., on the other hand, describes the use of wovensynthetic halogenated polymers as capacitor separators. The use of“hybrid” separators comprising polymer and paper material has also beendescribed. See, for example, U.S. Pat. No. 4,480,290 to Constanti etal., which describes the use of separators including a porous polymerfilm made from polypropylene or polyester and absorbent paper.

[0009] In the assembly of a capacitor cell it is important to maintainorientation, contact and, as applicable, alignment of the anode,cathode, and separator components. Failure to align these components maylead to short-circuiting or inefficient capacitor performance. Forexample, in cylindrical capacitors, proper spacing is typicallymaintained at the electrode edges or peripheries by providing separatoroverhang at the top and bottom of the anode and cathode winding, whichresults in a larger capacitor than would otherwise be necessary. Inaddition, the anode and cathode are precisely aligned and coiled tightlyby a winding machine to prevent movement of the anode, cathode, andseparator during subsequent processing and use. Alternatively, in flatcapacitors, anode to cathode alignment is typically maintained throughthe use of internal alignment posts. Build-up of static charge in theseparator material during manufacture of such capacitors can makehandling of the material particularly troublesome. All of thesetechniques have the disadvantage or requiring extra machinery orcapacitor components that would not otherwise be required.

[0010] It would be desirable to employ in capacitor cells, such asbatteries or capacitors, a separator material that is sufficiently thin,has strong tensile properties, possesses enhanced wettability andabsorption characteristics, is resistant to degradation in the cellenvironment, and has a precise porosity sufficient for use with aparticular capacitor cell.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The above and other objects and aspects of the invention will beapparent from the description of embodiments illustrated by thefollowing accompanying drawings:

[0012]FIG. 1 depicts a top perspective view of a portion of ananode/separator/cathode laminate;

[0013]FIG. 2 depicts a perspective view of an anode/separator/cathodelaminate partially formed into a circular, coiled position;

[0014]FIG. 3 depicts a perspective view of an anode/separator/cathodelaminate completely formed into a circular, coiled position;

[0015]FIG. 4 depicts a perspective view of an anode/separator/cathodelaminate formed into a flat, coiled position;

[0016]FIG. 5 depicts a side view of an anode/separator/cathode laminateformed into a flat, stacked position;

[0017]FIG. 6 depicts a side view of layers of separator materialpositioned between alternating anode and cathode layers;

[0018]FIG. 7 depicts a side cross sectional view of a strip of separatormaterial wrapped around alternating anode and cathode layers.

SUMMARY OF THE INVENTION

[0019] The present invention relates to capacitor cells and theutilization of separator materials that interact with one or moresurfactants in such cells. In various embodiments, the capacitor cell ofthe present invention comprises one or more anodes, one or more cathodesoperatively associated with the anodes, an electrolyte operativelyassociated with the anodes and the cathodes, one or more separatorsprovided in between the anodes and the cathodes to prevent internalelectrical short circuit conditions and to allow sufficient movement ofthe electrolyte within the capacitor cell and one or more surfactantsfor enhancing the wettability and absorption of the separators.

[0020] Generally, the separators utilized in the present inventioninclude one or more separator materials, such as nonwoven polymers,microporous polymers, track etched materials and papers. For example,the separators may include polyesters, polyethylene, polypropylene,polycarbonate, polytetrafluoroethylene, Kraft paper, Manila paper,NUCLEPORE®, CYCLOPORE™, ISOPORE™, PORETICS® and MEMTREX™, and SPI-Pore™or combinations thereof.

[0021] Additionally, capacitor cells according to the present inventionfurther include one or more surfactants for stimulating and enhancingthe wettability and/or absorption of the separator material. In someembodiments of the present invention, the separators are impregnatedwith the one or more surfactants. It is noted that the impregnatedseparators may also be optionally crosslinked with a crosslinkingreagent to thereby retain the surfactant within the separator material.Alternatively, the one or more surfactants may be mixed with theelectrolyte and interact with the separators upon administering theelectrolyte to the other components of the capacitor cell. Examples ofsurfactants utilized in the present invention include, but are notlimited to polyvinyl alcohol, dextran, agarose, alginate,polyacrylamide, polyglycidol, polyvinyl alcohol-co-polyethylene,poly(vinyl acetate-co-vinyl alcohol), polyacrylic acid, polyamide,polypeptides, poly-lysine, polyethyleneimine, poly-.beta.-malic acid,hyaluronic acid, derivatives of hyaluronic acid, polysaccharides,polyvinylpyrrolidone, and combinations or copolymers thereof.

[0022] The present invention also provides methods of making a capacitorcell that includes separators that interact with surfactants. In oneembodiment of the present invention the capacitor cell may be producedby first providing one or more separators, one or more anodes and one ormore cathode. It is noted that the separators may be administered withone or more surfactants to enhance the wettability and absorption of theseparators. As previously suggested the separators may be impregnatedwith the surfactants or exposed to the surfactants when contacted withan electrolyte. Once the separators, anodes (fully anodized in the caseof powdered metal anodes) and cathodes are present, the separators arepositioned between the anodes and cathodes so that the anodes andcathodes are unable to come in physical contact with each other. Forflat electrolytic and cylindrical type capacitors the alternating anodesand cathodes that are separated by separator material, are inserted intoa cell enclosure. An electrolyte is then placed into the cell enclosureto activate the anodes and cathodes. Finally, the enclosure is sealed toretain and maintain the separators, anodes, cathodes surfactants andelectrolyte within the enclosure.

[0023] The foregoing and additional advantages and characterizingfeatures of the present invention will become increasingly apparent tothose of ordinary skill in the art by references to the followingdetailed description and to the drawings.

DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention comprises a capacitor cell generallyincluding one or more cathodes, one or more anodes, one or moreseparators disposed between each anode and cathode pair, an electrolyteand one or more surfactants, which enhance the wettability andabsorption of the separator. More specifically, the capacitor cell ofthe present invention includes a separator that is impregnated with asurfactant or that absorbs and/or interacts with a surfactant to provideenhanced wettability and/or electrolyte absorption.

[0025] The separator utilized in the present invention may be producedfrom any suitable separator material including but not limited to 1)nonwoven polymers, such as polyesters, polystyrenes, aromaticpolyesters, polycarbonates, polyolefins, including polyethylene,polyethylene terephthalate, polypropylene, vinyl plastics such aspolyvinyl difluoride (PVDF), and cellulose esters such as cellulosenitrate, cellulose butyrate and cellulose acetate; 2) microporouspolymers such as polytetrafluoroethylene (PTFE); 3) track etch materials(track etched materials are explained further in the followingparagraphs); and papers, such as Kraft paper (cellulose) or Manilapaper.

[0026] A number of embodiments of the present invention utilizetrack-etched separators. The process of making track etched materials iswell known in the art and many variations of the process exist. Examplesof processes for forming track etched membranes are disclosed in U.S.Pat. Nos. 3,303,805; 3,493,751; 3,612,871; 6,120,875; 3,662,178;3,673,017; 3,677,844; 3,713,921; 3,802,972; 3,852,134; 4,855,049;4,956,219; 5,139,624; 5,449,917; 5,914,150, the entire contents of eachof which are incorporated herein by reference. The present separator canbe comprised of any material that has been track etched according to anyof the processes disclosed in the references above or according to anyknown track etching process.

[0027] While the material that is track etched can be any known materialthat is capable of being track etched, in preferred embodiments, theseparator material comprises a polymeric material. Polymeric materialsinclude but are not limited to polyesters, polystyrenes, aromaticpolyesters, polycarbonates, polyolefins, including polyethylene,polyethylene terephthalate, polypropylene, vinyl plastics such aspolyvinyl difluoride (PVDF), and cellulose esters such as cellulosenitrate, cellulose butyrate and cellulose acetate.

[0028] In particularly preferred embodiments, the track-etched materialcomprises a polycarbonate material. Polycarbonate materials arepreferred because they have outstanding impact resistance and toughness.They also have high tensile and structural strength. Commercialpolycarbonate materials are produced in various countries and are soldunder the trade names LEXAN, MERLON, MAKRAYLON, JUPILON, and PANLITE.Additionally, commercially available track-etched membranes include butare not limited to NUCLEPORE® and CYCLOPORE™ distributed by WhatMan,Inc. located in Newton, Mass., ISOPORE™ distributed by Millipore, Inc.located in Billerica, Mass., PORETICS® and MEMTREX™ distributed byOsmonics located in Minnetonka, Minn., and SPI-Pore™ distributed byStructure Probe, Inc. located in West Chester, Pa.

[0029] In one preferred embodiment, the separator is a pure cellulose,very low halide or chloride content Kraft paper having a thickness ofabout 0.0005 inches, a density of about 1.06 grams/cm.sup.3, adielectric strength of 1,400 ac Volts per 0.001 inches thickness, and alow number of conducting paths (about 0.4/ft² or less). When includingeither anode foil plates or cathode foil plates in conjunction withseparators, the separators are preferably cut slightly larger than thefoil plates to accommodate misalignment during the stacking ofseparators and foil plates and to prevent subsequent shorting betweenelectrodes of opposite polarity.

[0030] It is preferred that separators be formed of a material that: (a)is chemically inert; (b) is chemically compatible with the selectedelectrolyte; (c) may be impregnated with the electrolyte to produce alow resistance path between adjoining anode and cathode layers, and (d)physically separates adjoining anode and cathode layers. Separatorsutilized in embodiments of the present invention may also be formed ofmaterials other than Kraft paper, such as Manila paper, porous polymericmaterials or fabric gauze materials. For example, porous polymericmaterials may be disposed between anode and cathode layers, similar tothose disclosed in U.S. Pat. Nos. 3,555,369 and 3,883,784, in someembodiments of the present invention.

[0031] Preferably, the separators utilized in embodiments of the presentinvention have a thickness suitable for use in a capacitor cell. Therange of thicknesses of separators typically available for utilizationin capacitor cells of the present invention is approximately 250 micronsor less and preferably between 5-250 microns (or approximately0.0002-0.01 inches), most preferably 10-50 microns.

[0032] The capacitor cells of the present invention further include asurfactant, which enhances the wettability of the separator andincreases the separator's electrolyte absorption characteristics.Generally, the surfactants utilized in the cells of the presentinvention are either imbedded in the material during their constructionor applied after construction of the separator web. The surfactantsgenerally function in the cell to reduce the surface energy (wettingangle) of the separator material thereby allowing for better solvent orelectrolyte wetting (e.g. water). For example, in various embodiments ofthe present invention the surfactant makes the material more hydrophilicthereby lowering the contact angle between the electrolyte and thesurface of the material. This hydrophilic activity stimulates thewetting of the surfactant, which translates to better transmission ofions between the cathode and anode.

[0033] Any surfactant which enhances the wettability characteristics ofthe separator material may be utilized in the present invention. Forexample, polyvinyl alcohol, dextran, agarose, alginate, polyacrylamide,polyglycidol, polyvinyl alcohol-co-polyethylene, poly(vinylacetate-co-vinyl alcohol), polyacrylic acid, polyamide, polypeptides,poly-lysine, polyethyleneimine, poly-.beta.-malic acid, hyaluronic acid,derivatives of hyaluronic acid, polysaccharides andpolyvinylpyrrolidone, alone or in combination may be utilized assuitable surfactants with the capacitor cells of the present invention.

[0034] Additionally, as previously suggested the separators utilized inembodiments of the present invention may be impregnated with one or moresurfactants or may interact and absorb a surfactant that has been addedto the electrolyte. In one embodiment of the present invention separatormaterial, such as polymeric material, may be impregnated with one ormore surfactants during assembly of the separator material. For example,polymeric separators that are impregnated with one or more surfactantsmay be assembled by supplying the one or more surfactants to a mixtureof the corresponding monomers of the desired polymeric separator. Oncethe surfactants are added, the mixture can be polymerized, therebycapturing the surfactants within the separator material and henceimpregnating the separator material with one or more surfactants. Invarious embodiments of the present invention, the polymer/surfactantmixture may be extruded, during or after the polymerization process, toform the desired sheet configuration common to separators.

[0035] In an alternative embodiment separators may be impregnated withthe one or more surfactants by placing or dipping a layer of separatormaterial in a solution containing one or more surfactants and allowingthe separator material to adsorb the surfactants. For example, in apreferred embodiment, a solution comprised of a surfactant, such aspolyvinylpyrrolidone, is dissolved in a suitable solvent at aconcentration of about 0.001% to about 99.9%, preferably about 0.01% toabout 50%, more preferably about 1.0% to about 25%, and most preferablyabout 0.25% to about 5% and initially adsorbed onto the surfaces andoptionally into the porous spaces of a porous separator material simplyby dipping the separator material in the solution for about 0.05 minutesto about 20 minutes to permit physisorption of the surfactant to thesurfaces of the separator material. This impregnation process may beperformed utilizing other suitable surfactants including, but are notlimited to, polyvinyl alcohol, dextran, agarose, alginate,polyacrylamide, polyglycidol, polyvinyl alcohol-co-polyethylene,poly(aspartic acid), poly(ethyleneglycol-co-propyleneglycol), poly(vinylacetate-co-vinyl alcohol), polyacrylic acid, poly-B-malic acid),polyamide, polylysine, polyethyleneimine, and polysaccharides, or theircopolymers, either alone or in combination. Preferably, the surfactantcontains hydrophilic functional side groups on each monomer forattracting electrolyte.

[0036] Suitable solvents for the hydrophilic surfactants include, butare not limited to, methanol, ethanol, isopropanol, tetrahydrofuran,trifluoroacetic acid, acetone, water, dimethyl formamide (DMF), dimethylsulfoxide (DMSO), acetonitrile, benzene, hexane, chloroform, methylenechloride, supercritical carbon dioxide, or other compounds which solvatethe first layer.

[0037] For porous separator materials, excess adsorbed surfactant may berinsed from the surface of the separator material using fresh solvent toprevent bulk-deposited surfactant from partially blocking pores of theseparator material. Though optional, this step is preferred in order toensure that the pores of a porous separator material are not obstructedwith surfactant.

[0038] Once the surfactants are absorbed by the separator material, thesurfactants may optionally be cross-linked to themselves and/or theseparator material using a suitable cross-linking agent to assist inmaintaining the hydrophilic properties of the separator material. Thecrosslinking serves to greatly reduce or eliminate the potential fordesorption or migration of the surfactant. Suitable reagents for formingcross-linkages between surfactants and/or separator materials arecompounds comprised of at least two chemically functional groups, eitherhomofunctional or heterofunctional, that include, but are not limitedto, aldehydes, epoxides, acyl halides, alkyl halides, isocyanates,amines, anhydrides, acids, alcohols, haloacetals, aryl carbonates,thiols, esters, imides, vinyls, azides, nitros, peroxides, sulfones, andmaleimides, dissolved in solvents that wet the adsorbed layer. Inaddition, vinyl sulfone, succinyl chloride, polyanhydrides, poly-B-malicacid, ethylene glycolbis-succinimidyl succinate, succinimidylsuccinate-polyethylene glycol, and succinimidyl succinamide-polyethyleneglycol can also be used as cross-linking agents. Solvents suitable fordissolving the cross-linking reagent include, but are not limited to,acetone, water, alcohols, tetrahydrofuran (THF), dimethyl sulfoxide(DMSO), dimethyl formamide (DMF), benzene, acetonitrile, and dioxane.Other cross-linking reagents include, but are not limited to, freeradicals, anions, cations, plasma irradiation, electron irradiation, andphoton irradiation.

[0039] In a further embodiment of the present invention the one or moresurfactants may be added to the electrolyte wherein upon electrolytecontact with the separator the surfactants stimulate wettability andabsorption properties of the separator material. For example,polyethylene glycol and polyvinylpyrrolidone may be mixed to form asuitable electrolyte-surfactant mixture that provides enhancedwettability of the separator and better ion transmission

[0040] The separators and surfactants of the types described above canbe used in any capacitor cell. In certain embodiments, the abovedescribed separators and surfactants are used in a battery. For example,the battery may be a lithium battery. In lithium batteries, the anodecomprises lithium and the cathode comprises an active material such as,for example, carbon fluoride, a metal oxide, or a metal oxide bronze.More specifically, the battery may be a lithium silver vanadium oxidebattery. In this type of battery, the anode is comprised of lithium andthe cathode is comprised of silver vanadium oxide. An example of alithium silver vanadium oxide battery is described in U.S. Pat. No.6,130,005 to Crespi et al., the entire contents of which are hereinincorporated by reference.

[0041] In other embodiments, the above described separators andsurfactants are used in a capacitor. In one embodiment, the capacitormay be an electrolytic capacitor. More specifically, the capacitor maybe an aluminum electrolytic capacitor. In an electrolytic capacitor,both the anodes and cathodes are typically made of aluminum, preferablyaluminum foil. Generally, the anode foils are between about 0.008 toabout 0.001 inches thick. For example, in certain embodiments, eachanode foil comprises comparatively stiff, high purity aluminum foilabout 0.004 inches thick. Likewise, the cathode foils are between about0.005 to about 0.0005 inches thick. For example, in certain embodiments,each cathode foil comprises comparatively flexible, high purity aluminumfoil about 0.001 inches thick.

[0042] In yet other embodiments of the present invention the capacitorcell comprises a valve metal anode fabricated by pressing powdered metalinto a slug, sintering the slug, and then anodizing the slug. In thisembodiment the separator material is interposed between a fully formedanode and an adjacent volume of cathodic material. The fully formedanode may be configured in diverse shapes and thus, the separatormaterial should be adequately compliant as well as possess the otherdesirable properties described herein.

[0043] Other embodiments of the invention will now be described withreference to the drawings. The capacitor cell containing the abovedescribed separators and surfactants can be of any suitableconfiguration, for example a flat, cylindrical or, in the case ofpowdered valve metal capacitors, and arbitrary configuration. It is tobe understood that although the drawings primarily depict flat orcylindrical capacitor cells, the present invention is also specificallydirected to powdered valve metal capacitors. FIGS. 2-3 depict acapacitor cell formed in a cylindrical configuration. FIGS. 4-7 depict acapacitor cell formed in a flat construction. While the capacitor cellcan have any configuration, a flat configuration is preferred because itis typically smaller in design than a cylindrical configuration andcapable of operating within small medical devices, such asdefibrillators or pace makers.

[0044] The anode and cathode layers can be comprised of any electricallyconductive anode and cathode material known in the art to be used incapacitor cells. For example, typical anode materials include alkalimetals or alkali earth metals selected from Groups IA, IIA and IIIB fromthe Periodic Table of Elements. For example, these anode materialsinclude but are not limited to lithium, aluminum, sodium, potassium,calcium, magnesium, vanadium, tantalum, niobium or similar alloys orcombinations. Likewise, typical cathode materials include electricallyconductive metals include ruthenium, vanadium, copper, silver, chromium,bismuth, lead, tantalum, carbon, aluminum, magnesium, titanium, niobium,zirconium, zinc or similar alloys or combinations. These type of cathodematerials may be provided with a semiconductive or pseudocapacitivecoating. The coating may be an oxide, nitride, carbide, or carbonnitride.

[0045] In various embodiments of the present invention, both the anodesand cathodes are made of a metal foil, preferably thin metal foil. Metalfoil is particularly desirable because it is easily susceptible toetching and/or forming procedures. Such procedures are done to increasethe surface area of the anode or cathode material. An increase in thesurface area of either the anode or cathode often improves theperformance of the capacitor cell. For example, if the capacitor cell isa capacitor, the anode foil is typically processed to create a highcapacitance per unit area. Typically, the capacity of an electrolyticcapacitor is determined by the area of the anode surfaces and thethickness of the dielectric film covering this surface. As a result, anincrease in capacity can be obtained if the surface area of the anodelayer is increased.

[0046] A number of methods have been developed for increasing thesurface area of an anode or cathode material. Such methods include butare not limited to sand blasting, mechanical embossing, scratching withrotating brushes, use of abrasive materials, forming in rotary dies, andchemical etching. Each of these methods are well known in the art andany method can be used to increase the surface area of the anode orcathode. Preferably, a chemical etching procedure is used. Optimally,etching dissolves portions of the metal to create a dense network ofbillions of microscopic tunnels penetrating therethrough.

[0047] The anode, separator and cathode of the capacitor cell can beconfigured together in any suitable form. For example, in certainembodiments, the anode, separator, and cathode material can beconfigured together as strips laminated together. In other embodiments,the anode, separator, and cathode material can be configured as separatelayers of material. FIGS. 1-5 depict the anode, separator and cathodematerial in a laminate form. FIGS. 6-7 depict the anode, separator andcathode material in a layer form.

[0048]FIG. 1 depicts a portion of an anode/separator/cathode laminate.Generally, the laminate 10 comprises anode material 20, separatormaterial 50, such as an surfactant impregnated separator, and cathodematerial 30 adhered together. These materials can be adhered togetherusing any suitable adhesive, for example by using an ion-conductingadhesive. The laminate can be made by adhering an anode strip andcathode strip to each side of the separator. FIG. 1 specifically shows alaminate having an anode/separator/cathode/separator/anodeconfiguration. However, it should be apparent to one of skill in the artthat any number of anode, separator and cathode materials or strips ofmaterial can be used to form a suitable laminate. In addition, those ofskill in the art will readily recognize that the present invention isnot limited to adhesive electrode laminates, but should be construed toapply to any capacitor cell wherein an anode and a cathode requiringmechanical separation are disposed in a common enclosure adjacentelectrolyte. That is, the teaching of the present invention applies tobattery cells in addition to the capacitor cells used to exemplify thepresent invention.

[0049] The laminate 10 can be coiled or wrapped within a capacitor cellin any suitable configuration. For example, FIG. 2 depicts a laminate 10partially wrapped in a cylindrical coil position. FIG. 3 shows thelaminate 10 completely wrapped in a cylindrical coil position. Alsoshown in FIG. 3 are electrical connections 40, each extending from ananode strip 20 and a cathode strip 30. While laminates are typicallywrapped in a cylindrical coil position, this is not by any meansnecessary. For example, as shown in FIG. 4, the laminate 10 can bewrapped in a flat coil position. A flat coil position is particularlydesirable as it reduces the space necessary for containing the capacitorcell. FIG. 4 also shows electrical connections 40 extending from anodestrips 20 and cathode strips 30.

[0050] Likewise, while laminates are often coiled in position, otherconfigurations are available. For example, FIG. 5 depicts a laminate 10configured as a z-fold stacked configuration. Stacked configurations ofthe laminate 10 may be preferable over coiled configurations in order tooptimize packaging efficiency.

[0051]FIGS. 6 and 7 depict the anodes and cathodes configured asseparate layers or plates rather than a laminate sheet. In theseembodiments, each anode layer 20 and cathode layer 30 is a substantiallyrectangularly-shaped segments. However, it should be apparent that theanode layers 20 and cathode layers 30 can be configured in any suitableshape. The shapes of these layers are primarily a matter of designchoice, and are dictated largely by the shape, size, or configuration ofthe enclosure within which the layers are ultimately disposed. Also,each anode layer 20 and cathode layer 30 can be formed into a specific,predetermined shape using a die apparatus, such as that disclosed incommonly owned U.S. Pat. No. 6,006,133 to Lessar et al., the entirecontents of which are herein incorporated by reference. The shapes ofthe layers are primarily a matter of design choice, and are dictatedlargely by the shape or configuration of the cell enclosure within whichthose layers are disposed.

[0052] Likewise, the separator material 10 associated with the anodelayers 20 and cathode layers 30 can be configured in any arbitrary shapeto optimize packaging efficiency. For example, in FIG. 6, the separatorlayer 50 is configured as substantially rectangularly-shaped segmentsthat are disposed in between each anode and cathode layer. The separatorlayers 50 are typically longer than the anode layers 20 and cathodelayers 30 to ensure that proper separation is maintained. Alternatively,in FIG. 7, the separator material is configured as one long strip ofmaterial that is wrapped around the electrode layers. It should beapparent that the long strip of separator material can be wrapped aroundthe electrode layers in any suitable manner.

[0053] While in the embodiments depicted in the Figures, the anodes 20and cathodes 30 of the capacitor cell are generally configured as singlestrip (or layer) of metal, in certain embodiments, one or more of theanode strips (or layers) may comprise a double strip or double layerwith an electrically conductive strip (or layer) positioned in between.The electrically conductive strip (or layer) may be welded in betweenthe two anode strips (or layers). Preferably, the electricallyconductive strip (or layer) is made of aluminum metal.

[0054] It should also be understood by those skilled in the art that thelength of the anode/separator/cathode laminate used or that the precisenumber of anode and cathode layers selected for use in a given capacitorcell will depend on the energy density, volume, voltage, current, energyoutput and other requirements of the device. Similarly, it will beunderstood by those skilled in the art that the precise number ofnotched and un-notched anode layers, anode tabs, anode sub-assemblies,and cathode layers selected for use in a given capacitor cell willdepend upon the energy density, volume, voltage, current, energy outputand other requirements placed upon the capacitor cell.

[0055] All of the capacitor cell components are typically sealed withinan enclosure (not shown). The enclosure is preferably comprised of acorrosion-resistant metal such as stainless steel or titanium. Theenclosure is usually filled with a liquid electrolyte. In variousembodiments of the present invention, the capacitor cell may include anyelectrolyte solution suitable for use with a capacitor cell. Forexample, in embodiments where the capacitor cell comprises anelectrolytic capacitor, the electrolyte contains either a glycerol orglycol, as these render the capacitors operative over a much increasedtemperature range. For example, in certain embodiments, the electrolytesolution contains ethylene glycol or tetraethylene glycol dimethyl ether(“tetraglyme”).

[0056] In certain embodiments, the capacitor cell includes electricalconnections 40 extending from one or more anodes and cathodes. Theseelectrical connections 40 may pass through the enclosure to the outsideof the cell. Where the electrical connections 40 pass through theenclosure, they can be sealed against fluid leakage by adhesive bonding,heat sealing, heat molding, etc.

[0057] The present invention also provides methods for making acapacitor cell. The method generally comprises providing a separator ofthe type described above, and positioning on the separator material oneor more pairs of alternating cathode and anode plates or layers so thata separation is maintained between the anode and cathodes. Also, aspreviously disclosed the separator may be impregnated with one or moresurfactants. In positioning the separator within the cell, it isimportant to maintain contact and alignment of all anode, cathode, andseparator components. Failure in either aspect can lead toshort-circuiting or inefficient capacitor performance. Finally, theanode/separator/cathode assembly is enclosed in a case with one or moresuitable electrolytes.

[0058] Those of skill in the art will recognize that many of theembodiments and techniques provided by the present invention may beused, as applicable, to electrically isolate electrodes of diverseelectrochemical cells, such as primary and secondary battery cells. Thatis, the teaching of the present invention is not to be strictly limitedto capacitor cells but should be fairly construed to include other typesof electrochemical cells as set forth in the appended claims.

[0059] While the invention has been described in conjunction withspecific embodiments thereof, many alternatives, modifications, andvariations apparent to those skilled in the art in light of theforegoing description. Accordingly, the preceding disclosure is intendedto embrace all such alternatives, modifications, and variations, whichfall within the spirit and broad scope of the invention.

What is claimed is:
 1. A capacitor cell comprising: one or more anodes;one or more cathodes operatively associated with the anodes; anelectrolyte operatively associated with the anodes and the cathodes; oneor more separators provided in between the anodes and the cathodes toprevent internal electrical short circuit conditions and to allowsufficient movement of the electrolyte within the capacitor cell; andone or more surfactants disposed on at least a portion of the one ormore separators wherein the one or more surfactants enhance thewettability and absorption of the one or more separators.
 2. A capacitorcell according to claim 1 wherein the one or more separators include oneor more separator materials selected from the group consisting ofnonwoven polymers, microporous polymers, track etched materials andpapers.
 3. A capacitor cell according to claim 2 wherein the one or moreseparators include one or more separator materials selected from thegroup consisting of polyesters, polyethylene, polypropylene,polycarbonate, polytetrafluoroethylene, Kraft paper and Manila paper. 4.A capacitor cell according to claim 2 wherein the one or more separatorsinclude one or more track etched materials selected from the groupconsisting of NUCLEPORE®, CYCLOPORE™, ISOPORE™, PORETICS® and MEMTREX™,and SPI-Pore™.
 5. A capacitor cell according to claim 1 wherein the oneor more surfactants are selected from the group consisting of polyvinylalcohol, dextran, agarose, alginate, polyacrylamide, polyglycidol,polyvinyl alcohol-co-polyethylene, poly(vinyl acetate-co-vinyl alcohol),polyacrylic acid, polyamide, polypeptides, poly-lysine,polyethyleneimine, poly-.beta.-malic acid, hyaluronic acid, derivativesof hyaluronic acid, polysaccharides, polyvinylpyrrolidone, andcombinations or copolymers thereof.
 6. A capacitor cell according toclaim 1 wherein the one or more separators are impregnated with the oneor more surfactants.
 7. A capacitor cell according to claim 1 whereinthe one or more surfactants are mixed with the electrolyte.
 8. Acapacitor cell according to claim 6 wherein the one or more separatorsare crosslinked with a crosslinking reagent.
 9. A capacitor cellaccording to claim 8 wherein the crosslinking reagent is selected fromthe group consisting of aldehydes, epoxides, acyl halides, alkylhalides, isocyanates, amines, anhydrides, acids, alcohols, haloacetals,aryl carbonates, thiols, esters, imides, vinyls, azides, nitros,peroxides, sulfones, maleimides, vinyl sulfone, succinyl chloride,polyanhydrides, poly-B-malic acid, ethylene glycolbis-succinimidylsuccinate, succinimidyl succinate-polyethylene glycol, and succinimidylsuccinamide-polyethylene glycol.
 10. A capacitor cell according to claim1 wherein the capacitor cell is arranged in a substantially flat, coiledconfiguration.
 11. A capacitor cell according to claim 1 wherein thecapacitor cell is arranged in a cylindrical coiled configuration.
 12. Acapacitor cell according to claim 1 wherein the capacitor cell isarranged in a stacked configuration.
 13. A method of making a capacitorcell comprising: providing one or more separators, one or more anodesand one or more cathode; positioning the one or more separators inbetween the anodes and cathodes; administering one or more surfactantsto the one or more separators to enhance the wettability and absorptionof the one or more separators; inserting the positioned one or moreseparators, anodes and cathodes into a cell enclosure; administering anelectrolyte into the cell enclosure to activate the anodes and cathodes;and sealing the enclosure to retain and maintain the one or moreseparators, anodes, cathodes surfactants and electrolyte within theenclosure.
 14. A method according to claim 13 wherein the surfactantsare administered to the one or more separators by impregnating theseparators with the surfactants before positioning them between theanodes and cathodes.
 15. A method according to claim 14 wherein the oneor more separators impregnated with the surfactants is crosslinked witha crosslinking reagent.
 16. A method according to claim 15 wherein thecrosslinking reagent is selected from the group consisting of aldehydes,epoxides, acyl halides, alkyl halides, isocyanates, amines, anhydrides,acids, alcohols, haloacetals, aryl carbonates, thiols, esters, imides,vinyls, azides, nitros, peroxides, sulfones, maleimides, vinyl sulfone,succinyl chloride, polyanhydrides, poly-B-malic acid, ethyleneglycolbis->succinimidyl succinate, succinimidyl succinate-polyethyleneglycol, and succinimidyl succinamide-polyethylene glycol.
 17. A methodaccording to claim 13 wherein the one or more separators include one ormore separator materials selected from the group consisting of nonwovenpolymers, microporous polymers, track etched materials and papers.
 18. Amethod according to claim 17 wherein the one or more separators includeone or more separator materials selected from the group consisting ofpolyesters, polyethylene, polypropylene, polycarbonate,polytetrafluoroethylene, Kraft paper and Manila paper.
 19. A methodaccording to claim 17 wherein the one or more separators include one ormore track etched materials selected from the group consisting ofNUCLEPORE®, CYCLOPORE™, ISOPORE™, PORETICS® and MEMTREX™, and SPI-Pore™.20. A method according to claim 13 wherein the one or more surfactantsare selected from the group consisting of polyvinyl alcohol, dextran,agarose, alginate, polyacrylamide, polyglycidol, polyvinylalcohol-co-polyethylene, poly(vinyl acetate-co-vinyl alcohol),polyacrylic acid, polyamide, polypeptides, poly-lysine,polyethyleneimine, poly-.beta.-malic acid, hyaluronic acid, derivativesof hyaluronic acid, polysaccharides, polyvinylpyrrolidone, andcombinations or copolymers thereof.
 21. A method according to claim 13wherein the one or more surfactants are mixed with the electrolyte. 22.A method according to claim 13 further comprising arranging thecapacitor cell in a substantially flat, coiled configuration.
 23. Amethod according to claim 13 further comprising arranging the capacitorcell in a cylindrical coiled configuration.
 24. A method according toclaim 13 further comprising arranging the capacitor cell in a stackedconfiguration.